Produtividade de alface com o uso de diferentes fontes de matéria orgânica e efeito na fertilidade do solo.

Abstract

A field experiment was conducted in the Agrotécnica Federal de Crato School in an Oxissol to establish the dosage of chicken, cow and sheep manure that would supply the best yield of a lettuce crop. Single samples were collected in the depths of 0 – 20 cm, making a compound sample to characterize the soil. As organic fertilizers chicken, cow and sheep manure were used at the rates of 25%, 50%, 100%, 150% and 200% of the recommended dosage , in an experimental design using randomized blocks in a factorial arrangement of the order [(3 x 5) + 2], with three sources of organic matter at five levels, with two additional treatments, the first one with chemical fertilizer and the second one as an absolute control in four blocks, with one replicate per block totalizing 68 plots . After the preparation of the plots an application of the organic manures was made at the tested levels, 10 days before the transplant of the seedlings. The seedlings were planted in the spacing of 0,25m x 0,25m with the plots measuring 1,875m2 and with a useful area of 1,00m x 0,75m, with twelve plants per plot. Weeding was done when necessary and irrigation was done daily according to the crop needs. At 30 days after the beginning of the experiment the plants were harvested including the roots, when the second crop was planted , with 30 more days the third and 30 more , the fourth and 30 more the fifth crop were established . A soil sampling was made in each plot at the transplanting moment (zero time) and at 30 days of growth on the bed of each crop. In those samples the following analyses were run: organic carbon, total nitrogen, and available phosphorus and potassium. At harvest the plants fresh mass was measured by plot, and one plant was chosen for drying in an oven at 65 degrees Celsius and the dried matter by plant determined. The variables evaluated were subjected to analysis of variance, comparing the averages of the treatments by the Tukey test at the five percent probability level , and regression models were tested between the dependent variables an the levels of manure utilized. The chicken manure provided higher yields of lettuce in the first crop, being surpassed by the cow and sheep manures beginning with the second crop. In general, starting with the 100% recommendation the results are similar, with no justification of using higher dosages. In the third crop, the quality of the product was affected even at the highest dosages.